This invention relates to a seal ring for use in Stirling engines on high pressure compressors to seal high-pressurized working liquid under oil-less or non-lubricating conditions.
In a conventional composite seal ring as shown in FIGS. 1 and 2, an annular recess 3 is formed in an outer peripheral surface of a main seal ring 1' at a position opposite to the pressure side as indicated by P to provide an L-shaped cross-section, and an auxiliary seal ring 4' is fitted into the recess so as to misalign a gap portion 11 of the seal ring 1' with a gap portion 41 of the auxiliary seal ring 4'.
According to the various experiments, in the conventional composite seal ring, if the ring is applied to the Stirling engine or high pressure compressor under a non-lubricating and high pressure condition such as above 50 kg/cm.sup.2, a thin wall portion 12 of the L-shaped ring 1' is deformed into the gap portion 41 of the auxiliary seal ring 4' due to the high pressurized working liquid as shown in FIG. 3, whereby the gap 41 does not exhibit excellent sealing, and the sliding function of the auxiliary ring 4' with respect to an inner peripheral surface of a cylinder 5 may be degraded. Simultaneously, the auxiliary ring 4' may be deformed in wavy or corrugated configuration along the axial direction thereof, so that sealing performance in terms of upper and lower portions 13 and 14 of the rings may be deteriorated and these rings may not sustain adequate sealing during long use.